Method 1 -
Product of factors = N (number of factors/2))
let 6th factor = k
so k * 648 = N^3
so k * 3^4 * 2^3 = N^3
RHS is prefect cube so LHS shuld be perfect cube
so k = 3^2 = 9
Method2 : N = 2 * 3^2
648 = 1 * 2 * 3 * 6 * 18
remaining 9 so OA = 9

Here given E x E = E and A x A =A.
So E = 1 or 5, A = 5 or 1.
Let’s put E = 1 and A = 5.
5B1 = 1 x B1
Not possible.
Let’s put E = 5 and A = 1.
1B5 = 5 x B5
So B = 2.
BBA + CCD = EEE.
221 + CCD = 555.
1 + D = 5.
D = 4.
2 + C = 5.
C = 3.
AB x CE = 12 x 35 = 420.

At 3:30, the hour hand would be exactly between 3 and 4
=> 15 deg from both 3 and 4
At 3:30, the minute hand would be exactly at 6
The gap between the hour hand and the minute hand will be
30 deg (between 5 and 6) + 30 deg (between 4 and 5) + 15 deg (between hour hand and 4) = 75 degrees